Switch FlushCallback to be a PP_CompletionCallback....

cpp/device_context_2d.h

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef PPAPI_CPP_DEVICE_CONTEXT_2D_H_
 #define PPAPI_CPP_DEVICE_CONTEXT_2D_H_
 
 #include "ppapi/c/pp_stdint.h"
-#include "ppapi/c/ppb_device_context_2d.h"
 #include "ppapi/cpp/resource.h"
 
+typedef struct _pp_CompletionCallback PP_CompletionCallback;
 typedef struct _pp_Rect PP_Rect;
 
 namespace pp {
 
+class CompletionCallback;
 class ImageData;
 
 class DeviceContext2D : public Resource {
  public:
   // Creates an is_null() ImageData object.
   DeviceContext2D();
 
   // The copied device will refer to the original (since this is just a wrapper
   // around a refcounted resource).
   DeviceContext2D(const DeviceContext2D& other);
@@ skipping 21 matching lines @@
 
   // The browser will take ownership of the given image data. The object
   // pointed to by the parameter will be cleared. To avoid horrible artifacts,
   // you should also not use any other ImageData objects referring to the same
   // resource will no longer be usable. THIS COMMAND HAS NO EFFECT UNTIL YOU
   // CALL Flush().
   //
   // Please see PPB_DeviceContext2D.Swap for more details.
   bool ReplaceContents(ImageData* image);
 
-  // Flushes all the currently enqueued Paint, Scroll, and Swap commands. Can
-  // be used in synchronous mode (NULL callback pointer) from background
+  // Flushes all the currently enqueued Paint, Scroll, and Replace commands.
+  // Can be used in synchronous mode (NULL callback pointer) from background
   // threads.
   //
   // Please see PPB_DeviceContext2D.Flush for more details.
-  bool Flush(PPB_DeviceContext2D_FlushCallback callback, void* callback_data);
+  int32_t Flush(const CompletionCallback& cc);
 
  private:
   int32_t width_;
   int32_t height_;  
 };
 
 }  // namespace pp
 
 #endif  // PPAPI_CPP_DEVICE_CONTEXT_2D_H_